By way of background, the following terms will be used in this application with the meaning ascribed thereto.
The term “component defect” is used to mean that the apparatus can not attain or maintain a normal set point. In the context of a pump, a common component defect is often a leak but also encompasses the failure of sensing devices such as transducers or computing devices. As used herein, the term “leak” refers to a hole, crack or opening through which fluid escapes in a manner not intended by the user. The leak may be totally internal. That is, the fluid escapes from an area of high pressure to an area of low pressure within the apparatus. Or, such leak may be external, allowing fluid to escape from the confines of the hydraulic circuit. Leaking flammable fluids represent a safety concern, the detection of which would be very useful.
The term “solution failure” is used to suggest an absence of fluid, gases in solution or a partial filling of the pump assembly with fluid.
A “pump” is a mechanical device for moving fluids. Embodiments of the present invention have particular application to high pressure pumps used in analysis and diagnostics. By way of example, without limitation, pumps used in high performance liquid chromatography are capable of placing a fluid under as much as 10,000 psi. Such pumps can be single chamber pumps or multi-chambered pumps. One common multi-chambered pump is a serial pump in which a plurality of, usually two, pumping chambers are placed in series. That is, the flow of fluid first passes through a first pump chamber and then a second pump chamber. Another common multi-chambered pump is a parallel pump in which a plurality of, usually two, pumping chambers are placed in parallel. That is, fluid is received by a first chamber, which chamber brings the fluid to pressure and propels such fluid downstream without involving a further pump chamber. As the first pump chamber is exhausted, a second pump chamber starts to propel fluid. Parallel pumps are often equipped with rotary valves which control the outflow of the plurality of pump chambers.
As used herein, the term “control means” means control circuitry and/or computer programmable unit (CPU).
As used herein, “pressure measuring device” comprise any device for measuring pressure, including strain gauges and pressure transducers.
Valves are devices for closing, opening or directing fluid flow. Typical valves include such mechanical check valves and active valves. Mechanical check valves are responsive to pressure. Active valves receive a signal which directs power means, such as motors, solenoids and the like, to open or close the valve. Cycling valves are capable of selectively opening and closing the flow of fluid from one or more sources or directing the flow to one or more destinations. Cycling valves are used in parallel pumps to alternate the outlet flow from multiple pump chambers.
Current techniques require manual intervention to determine the integrity of a hydraulic system. It would be advantageous to have methods and apparatus capable performing operations which determine the presence or absence of a leak in a hydraulic system under pressure. Such methods and apparatus would be able to ascertain a problem in a system and alert the operator, or shut the operation down until the problem can be remedied.